Koen have already provided a bitbake recipe for trunk but if you wish to follow progress on my branch these are the steps you need to take.

If you wish to follow using git just open the xbmc_svn.bb and switch branch to gsoc-2010-beagleboard. The gsoc branch have all the required patches for crosscompilation so no need for patches. Set SRC_URI to:

Then all thats needed is to follow my branch is to change SRCREV to be the hash sum of the revision you wish to base from, this is kindof annoying to change all the time so I use a local git which I update instead.
Here I have cloned git repository from xbmc to /home/topfs/xbmc/ and using the following recipe http://pastebin.com/cF33fPhg